Fibrillar center

Close observations of immunofluorescence signals showed that there are three different staining patterns, which correspond to three different nucleolar compartments FC (Fibrillar center), DFC (dense fibrillar component), and GC (granular component). Nucleolus is surrounded by heterochromatin. When the cells are in very active state of its proliferation, the nucleolar compartments and heterochromatin are integrated into a highly intricate structure called nucleolonema . A recent study has suggested that the chromatin associated with the nucleolus is less mobile than... 

Fig.l Electron micrograph of an interphase nucleolus illustrating the component parts of fibrillar center (FC), dense fibrillar component (DFC), and granular component (GC). Scale bar, 0.5 /um. 

Fibrillar center Storage of inactive rDNA and proteins rDNA, RNA pol 1, UBF, topo I Scheer and Rose, 1984 Rendon et al., 1992 Raska et al., 1990b... 

Fibrillar centers were originally thought to be the interphase equivalence of mitotic chromosome NORs, but because there are many more FCs than the... 

Fig. 5 Antibody labeling of nucleolar component parts by iromunoelectron microscopy (a, c, and e) and indirect immunofluorescence (b, d, and f). (a and b) Fibrillar centers (FC) labeled with antibody to RNA polymerase I. (c and d) Dense fibrillar component (DFC) labeled with antibody to fibrillarin. (e and f) Granular component (GC) labeled with antibody to protein B23. (a, c, and e) Scale bar, 0.5 /urn. (b, d, and f) Scale bar, 5 /im.

Fig. 6 Distribution of flbrillar centers in PHA-stimulated human lymphocytes at 0 (a and d), 24 (b and e), and 48 hr (c and f) as visualized by conventional electron microscopy (a-c) and by indirect immunofluorescence (d-f) using a human autoantibody to RNA polymerase I. FC, Fibrillar center, DFC, dense flbrillar component G, granular component. The resting, unstimulated lymphocyte (a and d) contains a single large FC (arrowhead in d) that increases in number and decreases in size as the nucleolus grows in size with continued stimulation, (a-c) Scale bar, 0.5 /zm. (d-f) Scale bar, 5 /i.m.

Fig. 7 Electron microscopy of segregated nucleoli from cells treated with 0.1 jug/ml actinomycin D (a) or 25 /ig/ml DRB (b) for 4 hr. FC, Fibrillar center DFC, dense fibrillar component GC, granular component. Arrowhead (b) denotes a (ibrillar center. Scale bar, 0.5 tm.

Ochs, R. L., and Smetana, K. (1989). Fibrillar center distribution in nucleoli of PHA-stimulated human lymphocytes. Exp. Cell Res. 184, 552-557. 

Raska, 1., Dundr, M., Koberna, K., Melcak, 1., Risueno, M., and Torok, 1. (1995). Does the synthesis of ribosomal RNA take place within nucleolar fibrillar centers or dense fibrillar components A critical appraisal. J. Struct. BioL 114,1-22. 

Ordered body-centered cubic structures were observed by shearing aqueous gels made from anionic PtBS-PMANa block copolymer micelles [163]. The emergence of the ordered gel state could be accounted for similar building up of a polyelectrolyte-based fibrillar network that can be oriented under shear. 

FIGURE 2.17 Crystalline polymer structures formed under applied tension including flow conditions. The center shows the tertiary monofibriUar structure including platelets, the left shows these mono-fibrillar structures bundled together forming a quaternary structure fibril, and the right shows the distorted shish kebab formed with more rapid flow. 

Fig. 11 Craze in commercial polystyrene showing the characteristic steps nucleation through void formation in a pre-craze zone, growth of the fibrillar structure of the widening craze by drawing-in of new matrix material in the process zone, and final breakdown of the fibrillar matter transforming a craze into a crack (the crack front is more advanced in the center of the specimen, shielded by a curtain of unbroken fibrils marked by the arrow). The fibril thickness depends—of course—on the molecular variables, the strain rate-stress-temperature regime of the crazing sample and on its treatment (preparation, annealing) and geometry (solid, thin film) for PS typical values of between 2.5 and 30 nm are found [1,60,61]...

In terms of macrostructure, studies on the deformation of spherulites during biaxial orientation elucidated that spherulitic break-up occurs not only at their boundaries, but also at their centers. In either case and preferentially at higher temperatures, a fibrillar morphology was observed to develop at higher levels of stretching. Less data are available on direct methods to quantify the behavior of amorphous segments as they take part in these deformations. 

Projection of the electron density of coil and appended side chains upon a fibrillar cross section does not offer sufficiently sharp concentrations of density to lead to an expectation that much more than the 10.4 A. spacing between the major planes through protofibrillar centers will be strongly evident. The observed 4.6 A. spacing may well represent roughly the distances between atoms across the main chain coil, which are rendered variable in position and diffract almost independently in the very diffuse fashion observed, because of the irregularity of coil mentioned above. 

Figure 3.71 shows the change of average polystyrene phase diameter versus distance along the radial direction. The gradient phase structure was intensely related to the polystyrene content. With increasing amount of polystyrene, the size of the dispersed phase in the fiber center decreased continuously to nanosized fibrillar structure [257]. 

Cuajungco, M.R and Eaget, K.Y. 2003. Zinc takes the center stage Its paradoxical role in Alzheimer s disease. Brain Res. Brain Res. Rev. 41 44-56 Dahlgren, K.N., Manelli, A.M., Stine, W.B., Jn, Baker, L.K., Krafft, G.A. and LaDu, M.J. 2002. OUgomeric and fibrillar species of amyloid-P peptides differentieilly affect neuroneil viabUity. J. Biol. Chem. 277 32046-32053... 

Spherulite An aggregation of crystallites as a spherical cluster, consisting of fibrillar crystalline lamellae radiating from the center of the spherulite. 

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